System and method for managing reduced pressure at a tissue site

ABSTRACT

The illustrative embodiments described herein are directed to an apparatus and method for managing reduced pressure at a tissue site. The apparatus includes a reduced pressure source that generates reduced pressure. The reduced pressure is delivered to the tissue site via a delivery tube. The apparatus includes a single pressure sensor. The single pressure sensor detects an actual reduced pressure at the tissue site. The apparatus also includes a controller. The controller determines a responsiveness of the actual reduced pressure measured by the single pressure sensor to an increase in reduced pressure generated by the reduced pressure source. The apparatus includes an indicator. The indicator emits a signal when the controller determines that the actual reduced pressure measured by the single pressure sensor is nonresponsive to the increase in reduced pressure generated by the reduced pressure source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/900,556, filed Feb. 9, 2007, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of tissuetreatment, and more specifically to a system and method for applyingreduced pressure at a tissue site.

2. Description of Related Art

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. The treatment of woundsusing reduced pressure is sometimes referred to in the medical communityas “negative pressure tissue treatment,” “reduced pressure therapy,” or“vacuum therapy.” This type of treatment provides a number of benefits,including faster healing, and increased formulation of granulationtissue.

The reduced pressure at a tissue site caused by a reduced pressuretreatment system may need to be properly managed to maintain or increasethe effectiveness of the reduced pressure treatment. In addition, leaksand blockages in the components of the reduced pressure treatment systemmay need to be detected and corrected to maintain effective treatment.For example, a leak or blockage in the tube that connects a reducedpressure source, such as a vacuum pump, to the tissue site may disruptthe reduced pressure treatment being administered to the tissue site.The management or control of reduced pressure treatment systems may begenerally referred to as “pump pressure control” or “differentialpressure control.”

In one currently used pump pressure control system, pressure is measuredat the pump outlet and fed into a control system that drives a pump toachieve a target pressure at the outlet of the pump. However, the systemneglects any differential between the pressure measured at the pumpoutlet and the pressure in proximity to the tissue site because pressureis not measured at or near the tissue site. Thus, this currently usedpump pressure control system fails to provide information about leaks orblockages that occur between the tissue site and the pump.

Currently used differential pressure control systems employ two sensorsto measure pressure at both the pump outlet and at the tissue site. Thepressures measured by the two sensors are compared so that theoccurrence of leaks or blockages in reduced pressure treatment systemmay be identified. However, the two sensors used by current differentialpressure control systems increase the systems' size, weight, cost, andcomplexity. For example, the use of two sensors increases the amount ofelectronic circuitry and power used by the reduced pressure treatmentsystem. In addition, comparing measurements from two different sensorsrequires that the reduced pressure treatment system include circuitryand software for making the comparison. The additional componentsrequired by current differential pressure control systems reduce thosesystems' ability to be used to treat low-severity wounds and wounds onambulatory patients. In addition, the additional components increase theobtrusiveness and weight of the reduced pressure treatment system,thereby increasing the discomfort and limiting the mobility of thepatient.

BRIEF SUMMARY OF THE INVENTION

To alleviate the existing problems with reduced pressure treatmentsystems, the illustrative embodiments described herein are directed toan apparatus and method for managing reduced pressure at a tissue site.The apparatus includes a reduced pressure source that generates reducedpressure. The reduced pressure is delivered to the tissue site via adelivery tube. The apparatus includes a single pressure sensor. Thesingle pressure sensor detects an actual reduced pressure at the tissuesite. The apparatus also includes a controller. The controllerdetermines a responsiveness of the actual reduced pressure measured bythe single pressure sensor to an increase in reduced pressure generatedby the reduced pressure source. The apparatus includes an indicator. Theindicator emits a signal when the controller determines that the actualreduced pressure measured by the single pressure sensor is nonresponsiveto the increase in reduced pressure generated by the reduced pressuresource.

The illustrative embodiments also provide a method for managing reducedpressure at a tissue site. The process determines a target reducedpressure. The process detects an actual reduced pressure at the tissuesite using a single pressure sensor. The process compares the actualreduced pressure with the target reduced pressure to form a comparison.The process performs a reduced pressure management function based on thecomparison.

In another embodiment, the process increases a generated reducedpressure using a reduced pressure source. The process determines anactual reduced pressure at the tissue site using a single pressuresensor. The process emits a signal using an indicator in response to theactual reduced pressure at the tissue site being nonresponsive toincreasing the generated reduced pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an apparatus for managing reduced pressureat a tissue site in accordance with an illustrative embodiment of thepresent invention;

FIG. 2 is a perspective view of a multi-lumen tube in accordance with anillustrative embodiment of the present invention;

FIG. 3 is a perspective view of a multi-lumen tube in accordance with anillustrative embodiment of the present invention;

FIG. 4 is a flowchart illustrating a process for managing reducedpressure at a tissue site in accordance with an illustrative embodimentof the present invention;

FIG. 5 is a flowchart illustrating a process for managing reducedpressure at a tissue site in accordance with an illustrative embodimentof the present invention;

FIG. 6 is a flowchart illustrating a process for managing reducedpressure at a tissue site in accordance with an illustrative embodimentof the present invention; and

FIG. 7 is a flowchart illustrating a process for managing reducedpressure at a tissue site in accordance with an illustrative embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration specific preferredembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is understood that other embodiments maybe utilized and that logical structural, mechanical, electrical, andchemical changes may be made without departing from the spirit or scopeof the invention. To avoid detail not necessary to enable those skilledin the art to practice the invention, the description may omit certaininformation known to those skilled in the art. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claims.

The illustrative embodiments described herein provide and apparatus andmethod for managing reduced pressure at a tissue site. Reduced pressuregenerally refers to a pressure less than the ambient pressure at atissue site that is being subjected to treatment. In most cases, thisreduced pressure will be less than the atmospheric pressure of thelocation at which the patient is located. Although the terms “vacuum”and “negative pressure” may be used to describe the pressure applied tothe tissue site, the actual pressure applied to the tissue site may besignificantly less than the pressure normally associated with a completevacuum. Consistent with this nomenclature, an increase in reducedpressure or vacuum pressure refers to a relative reduction of absolutepressure, while a decrease in reduced pressure or vacuum pressure refersto a relative increase of absolute pressure.

The apparatus includes a reduced pressure source that generates reducedpressure. A reduced pressure source is any device capable of generatingreduced pressure. The reduced pressure is delivered to the tissue sitevia a delivery tube. The apparatus includes a single pressure sensor. Apressure sensor is any device capable of measuring or detecting apressure. The single pressure sensor detects an actual reduced pressureat the tissue site. In one embodiment, the single pressure sensor is theonly pressure sensor included in the apparatus.

The apparatus also includes a controller. A controller is any devicecapable of processing data, such as data from the single pressuresensor. A controller may also control the operation of one or morecomponents of the apparatus. The controller determines a responsivenessof the actual reduced pressure measured by the single pressure sensor toan increase in reduced pressure generated by the reduced pressuresource.

In one embodiment, the reduced pressure source generates a decreasedreduced pressure when the actual reduced pressure at the tissue sitedetected by the single pressure sensor exceeds a target reducedpressure. In another embodiment, the reduced pressure source generatesan increased reduced pressure when a target reduced pressure exceeds theactual reduced pressure at the tissue site detected by the singlepressure sensor.

The apparatus may also include a relief valve coupled to the deliverytube. A relief valve is any valve capable of decreasing the reducedpressure. In this embodiment, the relief valve may open to decrease theactual reduced pressure at the tissue site when the actual reducedpressure at the tissue site detected by the single pressure sensorexceeds a target reduced pressure by a predetermined threshold.

As used herein, the term “coupled” includes coupling via a separateobject. For example, the relief valve may be coupled to the deliverytube if both the relief valve and the relief tube are coupled to a thirdobject. The term “coupled” also includes “directly coupled,” in whichcase the two objects touch each other in some way. The term “coupled”also encompasses two or more components that are continuous with oneanother by virtue of each of the components being formed from the samepiece of material.

The apparatus includes an indicator. An indicator is any device capableof emitting a signal. For example, the indicator may emit a signal to auser of the apparatus. The indicator emits a signal when the controllerdetermines that the actual reduced pressure measured by the singlepressure sensor is nonresponsive to the increase in reduced pressuregenerated by the reduced pressure source. “Nonresponsive” may refer tothe lack of an effect on the actual reduced pressure, as measured by thesingle pressure sensor, from an increase in reduced pressure generatedby the reduced pressure source. Additional details regarding theresponsiveness of the actual reduced pressure measured by the singlepressure sensor are provided in the illustrative embodiments describedbelow.

The illustrative embodiments also provide a method for managing reducedpressure at a tissue site. The process determines a target reducedpressure. The target reduced pressure may be any reduced pressure thatis set by a user or the apparatus, such as the controller. The processdetects an actual reduced pressure at the tissue site using a singlepressure sensor. The process compares the actual reduced pressure withthe target reduced pressure to form a comparison. The process performs areduced pressure management function based on the comparison. A reducedpressure management function is any operation, function, or activity ofany or all of the components of the apparatus. For example, a reducedpressure management function may be performed by one or more componentsof the apparatus. A reduced pressure management function may also beperformed by a user.

In one embodiment, performing the reduced pressure management functionbased on the comparison includes decreasing a generated reduced pressuregenerated by a reduced pressure source in response to the actual reducedpressure exceeding the target reduced pressure.

In another embodiment, the process opens a relief valve that decreasesthe actual reduced pressure at the tissue site in response to the actualreduced pressure exceeding the target reduced pressure by apredetermined threshold. In another embodiment, the process eliminatesthe generated reduced pressure by turning off the reduced pressuresource in response to the actual reduced pressure exceeding the targetreduced pressure by a predetermined threshold.

In another embodiment, performing the reduced pressure managementfunction based on the comparison includes increasing a generated reducedpressure generated by a reduced pressure source in response to thetarget reduced pressure exceeding the actual reduced pressure. In thisembodiment, the process may emit a signal using an indicator in responseto the actual reduced pressure at the tissue site being nonresponsive toincreasing the generated reduced pressure.

In one example, the actual reduced pressure at the tissue site isnonresponsive to increasing the generated reduced pressure when theactual reduced pressure at the tissue site fails to increase within apredefined time period in response to increasing the generated reducedpressure. In another example, the actual reduced pressure at the tissuesite is nonresponsive to increasing the generated reduced pressure whenthe actual reduced pressure at the tissue site fails to meet a targetreduced pressure within a predefined time period in response toincreasing the generated reduced pressure. In a specific non-limitingexample, the predefined time period may be in a range of 4 to 6 seconds.

Turning now to FIG. 1, a block diagram of an apparatus for managingreduced pressure at a tissue site is depicted in accordance with anillustrative embodiment of the present invention. Specifically, FIG. 1shows reduced pressure treatment system 100 for managing the reducedpressure to tissue site 105.

Reduced pressure treatment system 100 may be used to apply reducedpressure treatment to tissue site 105. Tissue site 105 may be the bodilytissue of any human, animal, or other organism, including bone tissue,adipose tissue, muscle tissue, dermal tissue, vascular tissue,connective tissue, cartilage, tendons, ligaments, or any other tissue.While tissue site 105 may include a wound, diseased tissue, or defectivetissue, the tissue site may further include healthy tissue that is notwounded, diseased, or defective. The application of reduced pressure totissue site 105 may be used to promote the drainage of exudate and otherliquids from tissue site 105, as well as promote the growth ofadditional tissue. In the case in which tissue site 105 is a wound site,the growth of granulation tissue and removal of exudates and bacteriapromotes healing of the wound. The application of reduced pressure tonon-wounded or non-defective tissue, including healthy tissue, may beused to promote the growth of tissue that may be harvested andtransplanted to another tissue location.

The reduced pressure that is applied to tissue site 105 is generated byreduced pressure source 110. Reduced pressure source 110 may be any typeof manually, mechanically, or electrically operated pump. Non-limitingexamples of reduced pressure source 110 include devices that are drivenby stored energy, and which are capable of producing a reduced pressure.Examples of these stored energy, reduced pressure sources include,without limitation, pumps driven by piezo electric energy, springenergy, solar energy, kinetic energy, energy stored in capacitors,combustion, and energy developed by Sterling or similar cycles. Otherexamples of reduced pressure source 110 include devices that aremanually activated, such as bellows pumps, peristaltic pumps, diaphragmpumps, rotary vane pumps, linear piston pumps, pneumatic pumps,hydraulic pumps, hand pumps, foot pumps, and manual pumps such as thoseused with manually-activated spray bottles. Still other devices andprocesses that may be used or included in reduced pressure source 110include syringes, lead screws, ratchets, clockwork-driven devices,pendulum-driven devices, manual generators, osmotic processes, thermalheating processes, and processes in which vacuum pressures are generatedby condensation.

In another embodiment, reduced pressure source 110 may include a pumpthat is driven by a chemical reaction. A tablet, solution, spray, orother delivery mechanism may be delivered to the pump and used toinitiate the chemical reaction. The heat generated by the chemicalreaction may be used to drive the pump to produce the reduced pressure.In another embodiment, a pressurized gas cylinder such as a CO₂ cylinderis used to drive a pump to produce the reduced pressure. In stillanother embodiment, reduced pressure source 110 may be a battery-drivenpump. Preferably, the pump uses low amounts of power and is capable ofoperating for an extended period of time on a single charge of thebattery.

Reduced pressure source 110 provides reduced pressure to tissue site 105via dressing 115. Dressing 115 includes manifold 120, which may beplaced to adjacent to or in contact with tissue site 105. Manifold 120may be a biocompatible, porous material that is capable of being placedin contact with tissue site 105 and distributing reduced pressure to thetissue site 105. Manifold 120 may be made from foam, gauze, felted mat,or any other material suited to a particular biological application.Manifold 120 may include a plurality of flow channels or pathways tofacilitate distribution of reduced pressure or fluids to or from tissuesite 105.

In one embodiment, manifold 120 is a porous foam and includes aplurality of interconnected cells or pores that act as flow channels.The porous foam may be a polyurethane, open-cell, reticulated foam suchas GranuFoam manufactured by Kinetic Concepts, Inc. of San Antonio, Tex.If an open-cell foam is used, the porosity may vary, but is preferablyabout 400 to 600 microns. The flow channels allow fluid communicationthroughout the portion of manifold 120 having open cells. The cells andflow channels may be uniform in shape and size, or may include patternedor random variations in shape and size. Variations in shape and size ofthe cells of manifold result in variations in the flow channels, andsuch characteristics may be used to alter the flow characteristics offluid through manifold 120.

In one embodiment, manifold 120 may further include portions thatinclude “closed cells.” These closed-cell portions of manifold 120contain a plurality of cells, the majority of which are not fluidlyconnected to adjacent cells. Closed-cell portions may be selectivelydisposed in manifold 120 to prevent transmission of fluids throughperimeter surfaces of manifold 120.

Manifold 120 may also be constructed from bioresorbable materials thatdo not have to be removed from a patient's body following use of reducedpressure treatment system 100. Suitable bioresorbable materials mayinclude, without limitation, a polymeric blend of polylactic acid (PLA)and polyglycolic acid (PGA). The polymeric blend may also includewithout limitation polycarbonates, polyfumarates, and caprolactones.Manifold 120 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with manifold 120 topromote cell-growth. A scaffold is a substance or structure used toenhance or promote the growth of cells or formation of tissue, such as athree-dimensional porous structure that provides a template for cellgrowth. Illustrative examples of scaffold materials include calciumphosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, orprocessed allograft materials. In one example, the scaffold material hasa high void-fraction (i.e. a high content of air).

In other embodiments, the manifold 120 may be formed from poroushydrogels or hydrogel-forming materials, textiles, such as fabrics,ceramics, laminates, biologics, biopolymers, corks, and hemostaticdressings. Alternatively, beads may be placed in contact with the tissuesite 105 and used to distribute reduced pressure.

Dressing 115 also includes sealing member 125. Manifold 120 may besecured to tissue site 105 using sealing member 125. Sealing member 125may be a cover that is used to secure manifold 120 at tissue site 105.While sealing member 125 may be impermeable or semi-permeable, in oneexample sealing member 125 is capable of maintaining a reduced pressureat tissue site 105 after installation of the sealing member 125 overmanifold 120. Sealing member 125 may be a flexible drape or film madefrom a silicone based compound, acrylic, hydrogel or hydrogel-formingmaterial, or any other biocompatible material that includes theimpermeability or permeability characteristics desired for tissue site105. Sealing member 125 may be formed of a hydrophobic material toprevent moisture absorption by the sealing member 125.

Instead of being provided in “sheet” form such as that of a drape,sealing member 125 may be provided in a pourable or sprayable form thatis applied over the manifold 120 after placement of manifold 120 incontact with the tissue site 105. Similarly, sealing member 125 mayinclude a device that is placed over manifold 120 and tissue site 105 toprovide sealing functionality, including but not limited to a suctioncup, a molded cast, and a bell jar.

In one embodiment, sealing member 125 is configured to provide a sealedconnection with the tissue surrounding manifold 120 and tissue site 105.The sealed connection may be provided by an adhesive positioned along aperimeter of sealing member 125 or on any portion of sealing member 125to secure sealing member 125 to manifold 120 or the tissue surroundingtissue site 105. The adhesive may be pre-positioned on sealing member125 or may be sprayed or otherwise applied to sealing member 125immediately prior to installing sealing member 125.

As an alternative to an adhesive sealant, a sealed connection may beprovided by circumferentially wrapping the area adjacent to tissue site105 with sealing member 125. For example if tissue site 105 is locatedon an extremity of a patient, an elongated drape or “drape tape” couldbe wrapped multiple times around manifold 120 and the area surroundingtissue site 105 to provide the sealed connection. Alternatively, thesealed connection between sealing member 125 and the tissue surroundingtissue site 105 may be provided by reduced pressure applied by reducedpressure treatment system 100. In this embodiment, the perimeter ofsealing member 125 could be “vacuum” sealed to a patient's skin. Instill another embodiment, sealing member 125 may be sutured to thetissue surrounding tissue site 105 to provide a sealed connection.

In some cases, sealing member 125 may not be required to seal tissuesite 105. For example, tissue site 105 may be capable of being“self-sealed” to maintain reduced pressure. In the case of subcutaneousand deep tissue wounds, cavities, and fistulas, maintenance of reducedpressure at tissue site 105 may be possible without the use of sealingmember 125. Since tissue often encases or surrounds these types oftissue sites, the tissue surrounding the tissue site acts effectively asa sealing member.

The reduced pressure generated by reduced pressure source 110 may beapplied to tissue site 105 using source tube 130 and delivery tube 135.Source tube 130 and delivery tube 135 may be any tube through which agas, liquid, gel, or other fluid may flow. For example, exudate fromtissue site 105 may flow through delivery tube 135. In FIG. 1, sourceline 130 couples reduced pressure source 110 to canister 140 anddelivery tube 135 couples canister 140 to dressing 115. However, inanother embodiment, reduced pressure source 135 may be directly coupledto dressing 115 using delivery tube 135.

Source tube 130 and delivery tube 135 may be made from any material.Source tube 130 and delivery tube 135 may be either flexible orinflexible. Also, source tube 130 and delivery tube 135 may include oneor more paths or lumens through which fluid may flow. For example,delivery tube 135 may include two lumens. In this example, one lumen maybe used for the passage of exudate from tissue site 105 to canister 140.The other lumen may be used to deliver fluids, such as air,antibacterial agents, antiviral agents, cell-growth promotion agents,irrigation fluids, or other chemically active agents, to tissue site105. The fluid source from which these fluids originate is not shown inFIG. 1. Additional details regarding the inclusion of multi-lumen tubesin reduced pressure treatment system 100 are provided below.

In one embodiment, delivery tube 135 is coupled to manifold 120 viaconnection member 145. Connection member 145 permits the passage offluid from manifold 120 to delivery tube 135, and vice versa. Forexample, exudates collected from tissue site 105 using manifold 120 mayenter delivery tube 135 via connection member 145. In anotherembodiment, reduced pressure treatment system 100 does not includeconnection member 145. In this embodiment, delivery tube 135 may beinserted directly into sealing member 125 or manifold 120 such that anend of delivery tube 135 is adjacent to or in contact with manifold 120.

Reduced pressure treatment system 100 includes canister 140. Liquid,such as exudate, from tissue site 105 may flow through delivery tube 135into canister 140. Canister 115 may be any device or cavity capable ofcontaining a fluid, such as gases and liquids, as well as fluids thatcontain solids. For example, canister 115 may contain exudates fromtissue site 105. Source tube 130 and delivery tube 135 may be directlyconnected to canister 140, or may be coupled to canister 140 via aconnector, such as connector 150.

The canister 140 may be a flexible or rigid canister, a bag, or pouchfluidly connected to manifold 120 by delivery tube 135. Canister 140 maybe a separate container or may be operably combined with reducedpressure source 110 to collect exudate and fluids. In an illustrativeembodiment in which a manual pump, such as a bellows pump, is used asreduced pressure source 110, the variable-volume chamber that generatesthe reduced pressure may also serve as canister 140, collecting fluid asthe chamber expands. The canister 140 may include a single chamber forcollecting fluids, or alternatively may include multiple chambers. Adesiccant or absorptive material may be disposed within canister 140 totrap or control fluid once the fluid has been collected. In the absenceof canister 140, a method for controlling exudate and other fluids maybe employed in which the fluids, especially those that are watersoluble, are allowed to evaporate from manifold 120.

Reduced pressure treatment system 100 includes pressure sensor 155.Pressure sensor 155 detects an actual reduced pressure at tissue site105. In one non-limiting example, pressure sensor 155 is a siliconpiezoresistive gauge pressure sensor. In one embodiment, pressure sensor155 is the only pressure sensor included in reduced pressure treatmentsystem 100. In this embodiment, reduced pressure treatment system 100includes no other pressure sensor other than pressure sensor 155.

Pressure sensor 155 detects the reduced pressure at tissue site 105 viacontrol tube 160. Control tube 160 is any tube through which a gas mayflow. Control tube 160 may be made from any material. Control tube 160may be either flexible or inflexible. Also, control tube 160 may includeone or more paths or lumens through which fluid may flow.

In FIG. 1, control tube 160 is shown as passing through connector 150.However, the placement of control tube 160 may be varied to accommodateparticular needs and applications. For example, control tube 160 may berouted through canister 140, along an outside surface of canister 140,or may bypass canister 140. The end of control tube 160 that is oppositeof pressure sensor 155 may be coupled to manifold 120 via connector 145.In another example, control tube 160 may be inserted directly intosealing member 125 or manifold 120 such that an end of control tube 160is adjacent to or in contact with manifold 120.

In another embodiment, delivery tube 135 and control tube 160 are eachlumens in a single multi-lumen tube. Source tube 130 and control tube160 may also each be lumens in a single multi-lumen tube. In the examplein which reduced pressure source 110 is coupled to manifold 120 usingonly delivery tube 135, a single multi-lumen tube may be used to coupleboth reduced pressure source 110 and pressure sensor 155 to manifold120. Additional details regarding the multi-lumen embodiments will beprovided below in FIGS. 2 and 3.

Pressure sensor 155 may be located anywhere on reduced pressuretreatment system 100. In FIG. 1, pressure sensor 155 is shown to beremote from tissue site 105. In this example, the reduced pressure attissue site 105 may be detected from remotely located pressure sensor155 through control tube 160, which permits the flow of gas. Also inthis example, pressure sensor may be directly or indirectly coupled toother remotely located components of reduced pressure treatment system100, such as reduced pressure source 110, canister 140, or any otherillustrated component of reduced pressure treatment system 100. Inanother example, pressure sensor 155 may be placed adjacent to tissuesite 155. In this example, pressure sensor 155 may not require the useof control tube 160 to detect the pressure at tissue site 105. In onenon-limiting example, pressure sensor 155 is directly coupled tomanifold 120 or placed between sealing member 125 and manifold 120.

Reduced pressure treatment system 100 includes control tube valve 165.Control tube valve 165 may be coupled to control tube 160. Control tubevalve 165 may be any valve capable of relieving the reduced pressure incontrol tube 160. Non-limiting examples of control tube valve 165include a pneumatic solenoid valve, a proportional valve, or amechanical valve.

In one example, control tube valve 165 may be manually controlled by ahuman being. In another example, control tube valve 165 may becontrolled by controller 170. In one embodiment, control tube valve 165may be opened to relieve the reduced pressure in control tube 160 when ablockage is detected in control tube 160. Such a blockage may occur, forexample, when exudate or other fluid from tissue site 105 clogs controltube 160. By relieving the reduced pressure in control tube 160 viacontrol tube valve 165, the blockage may be cleared from control tube160.

Reduced pressure treatment system 100 also includes relief valve 175.Relief valve 175 may be a valve that is coupled to any one of or anycombination of source tube 130, canister 140, connector 150, deliverytube 135, connector 145, reduced pressure source 110, or dressing 115.Relief valve 175 may any type of valve capable of relieving the reducedpressure at tissue site 105. Non-limiting examples of relief valve 175include a pneumatic solenoid valve, a proportional valve, or amechanical valve. In one example, relief valve 175 may be opened torelieve the reduced pressure at tissue site 105. Relief valve 175 mayalso be used to manage the reduced pressure at tissue site 105.Additional details regarding the use of relief valve 175 and othercomponents of the reduced pressure treatment system 100 to manage thereduced pressure at tissue site 105 are provided below.

Reduced pressure treatment system includes controller 170. Controller170 is any device capable of processing data, such as data from pressuresensor 155. Controller 170 may also control the operation of one or morecomponents of reduced pressure treatment system 100, such as reducedpressure source 110, relief valve 175, control tube valve 165, pressuresensor 155, or indicator 180. In one embodiment, controller 170 receivesand processes data, such as data from pressure sensor 155, and controlsthe operation of one or more components of reduced pressure treatmentsystem 100 to manage the reduced pressure at tissue site 105.

In one embodiment, controller 170 determines a target reduced pressurefor tissue site 105. The target reduced pressure may be a user-definablereduced pressure for tissue site 105. The target reduced pressure mayalso be determined by controller 170. In one example, the target reducedpressure is a reduced pressure that provides an effective treatment oftissue site 105 and takes into account safety issues associated withapplying reduced pressure to tissue site 105.

In one example, pressure sensor 155 detects the reduced pressure attissue site 105. The reduced pressure measurement may be received bycontroller 170 from pressure sensor 155. Controller 170 may compare thereduced pressure received from pressure sensor 155 with the targetreduced pressure to form a comparison. Controller 170 may then performor direct a component of reduced pressure treatment system 100 toperform a reduced pressure management function based on the comparison.

In one embodiment, controller 170, in performing the reduced pressuremanagement function based on the comparison, decreases a generatedreduced pressure generated by reduced pressure source 110 in response tothe actual reduced pressure exceeding the target reduced pressure. Forexample, if reduced pressure source 110 is a motorized or otherwiseelectrically operated reduced pressure source, the motor or electricalprocess may be slowed such that reduced pressure source 110 generates adecreased amount of reduced pressure. In another non-limiting example,if reduced pressure source 110 is a chemically driven reduced pressuresource, the chemical process driving reduced pressure source 110 may beslowed or altered to decrease the amount of reduced pressure generatedby reduced pressure source 110.

In another embodiment, controller 170 opens relief valve 175 to decreasethe reduced pressure at tissue site 105 in response to the actualreduced pressure, as measured by pressure sensor 155, exceeding thetarget reduced pressure by a predetermined threshold. The predeterminedthreshold may be determined by a user or by a component of reducedpressure treatment system 100, such as controller 170. In one example,the predetermined threshold is a threshold that helps to ensure thesafety of tissue at tissue site 105. For example, the predeterminedthreshold may be determined such that an actual reduced pressure attissue site 105 that exceeds the target reduced pressure by thepredetermined threshold may affect the safety of tissue at tissue site105. Thus, this embodiment may be implemented as a safety mechanismusing the single pressure sensor 155.

In another embodiment, controller 170 turns off or shuts down reducedpressure source 110 in response to the actual reduced pressure, asmeasured by pressure sensor 155, exceeding the target reduced pressureby a predetermined threshold. Turning off or shutting down reducedpressure source 110 decreases the reduced pressure at tissue site 105.In one example, the predetermined threshold beyond which reducedpressure source 110 is turned off is greater than or less than thepredetermined threshold beyond which relief valve 175 is opened asdescribed in the previous embodiment. Thus, in this example, atwo-tiered safety mechanism is employed to ensure the safety of tissueat tissue site 105. In another example, the predetermined thresholdbeyond which reduced pressure source 110 is turned off is the same asthe predetermined threshold beyond which relief valve 175 is opened.

In another example, controller 170, in performing the reduced pressuremanagement function based on the comparison, increases a generatedreduced pressure generated by reduced pressure source 110. For example,if reduced pressure source 110 is a motorized or otherwise electricallyoperated reduced pressure source, the pace of the motor or electricalprocess may be increased such that reduced pressure source 110 generatesan increased amount of reduced pressure. In another non-limitingexample, if reduced pressure source 110 is a chemically driven reducedpressure source, the chemical process driving reduced pressure source110 may be hastened or altered to increase the amount of reducedpressure generated by reduced pressure source 110.

In another embodiment, controller 170 determines a responsiveness of theactual reduced pressure at tissue site 105, as measured by pressuresensor 155, to an increase in the generated reduced pressure fromreduced pressure source 110. In one example, controller 170 may detectwhen the reduced pressure generated by reduced pressure source isincreased or decreased. For example, controller 170 may be able todetect when the motor speed, chemical reaction speed, or compressionspeed of reduced pressure source 110 has increased or decreased. Otherparameters that may be detected by controller 170 to determine such anincrease or decrease include the current draw of a motor, which mayindicate the pump's duty. The level of power or pulse-width modulationrequired to be given to the motor to deliver the required reducedpressure to tissue site 105 may also be detected. Controller 170 mayalso be able to infer that the reduced pressure generated by reducedpressure source is increased or decreased based on the comparisonbetween the actual reduced pressure measured by pressure sensor 155 andthe target reduced pressure.

In one embodiment, controller 170 directs indicator 180 to emit a signalin response to the actual reduced pressure at tissue site 105, asmeasured by pressure sensor 155, being nonresponsive to increasing thegenerated reduced pressure. In one embodiment, indicator 180 is a lightemitting diode, or “LED.” In this embodiment, indicator 180 illuminatesin response to the actual reduced pressure at tissue site 105 beingnonresponsive to increasing the generated reduced pressure.

In another embodiment, indicator 180 is a sound emitting device, such asa speaker. In this embodiment, indicator 180 emits a sound in responseto the actual reduced pressure at tissue site 105 being nonresponsive toincreasing the generated reduced pressure.

In another embodiment, the actual reduced pressure at tissue site 105 isnonresponsive to increasing the generated reduced pressure when theactual reduced pressure at tissue site 105 fails to increase within apredefined time period in response to increasing the generated reducedpressure. Such nonresponsiveness may indicate that one or morecomponents of reduced pressured treatment system 100, such as deliverytube 135 or source tube 130, are blocked or have a leak. For example,liquid, such as exudate, from tissue site 105 may have clogged deliverytube 135 or source tube 130. In another example, a rupture may haveoccurred at a location along delivery tube 135 or source tube 130.

The predefined time period may be any time period, and may be set by auser of reduced pressure treatment system 100, or a component of reducedpressure treatment system 100, such as controller 170. In one example,the predefined time period in a range of one second to ten seconds orfour seconds to six seconds. In one specific non-limiting example, thepredefined time period is five seconds.

In another embodiment, the actual reduced pressure at tissue site 105 isnonresponsive to increasing the generated reduced pressure when theactual reduced pressure at tissue site 105 fails to meet a targetreduced pressure within a predefined time period in response toincreasing the generated reduced pressure. Similar to the previouslydescribed embodiment, such nonresponsiveness may indicate that one ormore components of reduced pressured treatment system 100, such asdelivery tube 135 or source tube 130, are blocked or have a leak.

In another embodiment of the present invention, if reduced pressuresource 110 is a vacuum pump and motor, a sensor may be coupled to thevacuum pump or motor to measure the pump or motor speed. Themeasurements acquired by the sensor may be used to infer the pressuredelivered by the pump, thereby providing a mechanism for determiningwhether leaks or blockages are present and distinguishing between them.For example, detection of leaks may be performed by monitoring the speedof either or both of the pump or motor. If a leak occurs while reducedpressure treatment is being administered, either or both of the pumpspeed or motor speed will likely increase indicating that the pump isgenerating more reduced pressure. If a blockage occurs, the speed ofeither or both of the pump or motor will likely decrease. The outputfrom the pump or motor speed sensor may be used by controller 170 toemit a signal using indicator 180 during a leak or blockage condition.

In one specific illustrative example, reduced pressure source 110includes a motor having a speed. In this example, a sensor may detectthe speed of the motor. Indicator 180 may emit a signal when the speedof the motor changes by a threshold amount. The threshold amount may beany amount, and may be set by a user of reduced pressure treatmentsystem 100, or a component of reduced pressure treatment system 100,such as controller 170. The threshold amount may be expressed in termsof a finite quantity, a percentage, or any combination thereof.

Turning now to FIG. 2, a perspective view of a multi-lumen tube isdepicted in accordance with an illustrative embodiment of the presentinvention. Specifically, FIG. 2 depicts multi-lumen tube 200, which maybe implemented in a reduced pressure treatment system, such as reducedpressure treatment system 100 in FIG. 1.

Multi-lumen tube 200 includes two lumens. Specifically, multi-lumen tube200 includes lumens 235 and 260. Although multi-lumen tube 200 includestwo lumens 235 and 160, multi-lumen tube may have any number of lumens,such as three, four, or ten.

In one embodiment, one of lumens 235 and 260, such as lumen 235, is adelivery tube or source tube, such as delivery tube 135 and source tube130 in FIG. 1. In another embodiment, one of lumens 235 and 260, such aslumen 260, is a control tube, such as control tube 160 in FIG. 1. Byincorporating a combination of a delivery tube, source tube, and controltube as lumens in a single multi-lumen tube, the number of separatetubes included in the reduced pressure treatment system may be reduced.The reduced number of tubes simplifies the reduced pressure treatmentsystem for use by a user, and lessens the burden of carrying the reducedpressure treatment system.

Turning now to FIG. 3, a perspective view of a multi-lumen tube isdepicted in accordance with an illustrative embodiment of the presentinvention. Specifically, FIG. 3 depicts multi-lumen tube 300, which maybe implemented in a reduced pressure treatment system, such as reducedpressure treatment system 100 in FIG. 1. Multi-lumen tube 300 may be anon-limiting example of multi-lumen tube 200 in FIG. 2.

Multi-lumen tube 300 includes nine lumens. Specifically, multi-lumentube 300 includes lumen 335 and peripheral lumens 360. Althoughmulti-lumen tube 300 shows peripheral lumens 360 as encircling lumen335, the lumens in multi-lumen tube 300 may have any spatialconfiguration relative to one another.

In one embodiment, one of lumens 335 and 360, such as lumen 335, is adelivery tube or source tube, such as delivery tube 135 and source tube130 in FIG. 1. In another embodiment, one of lumens 335 and 360, such asany or all of lumens 360, is a control tube, such as control tube 160 inFIG. 1. Similar to multi-lumen tube 300 in FIG. 3, by incorporating anycombination of a delivery tube, source tube, and control tube as lumensin multi-lumen tube 300, the number of separate tubes included in thereduced pressure treatment system may be reduced to increase theusability of the reduced pressure treatment system in which themulti-lumen tube is included.

Turning now to FIG. 4, a flowchart illustrating a process for managingreduced pressure at a tissue site is depicted in accordance with anillustrative embodiment of the present invention. The processillustrated in FIG. 4 may be implemented by a controller, such ascontroller 170 in FIG. 1, in conjunction with other components of areduced pressure treatment system, such as components of reducedpressure treatment system 100 in FIG. 1.

The process begins by determining a target reduced pressure (step 405).The process detects an actual reduced pressure at a tissue site using asingle pressure sensor (step 410). The process compares the actualreduced pressure with the target reduced pressure to form a comparison(step 415). The process performs a reduced pressure management functionbased on the comparison (step 420).

Turning now to FIG. 5, a flowchart illustrating a process for managingreduced pressure at a tissue site is depicted in accordance with anillustrative embodiment of the present invention. The processillustrated in FIG. 5 may be implemented by a controller, such ascontroller 170 in FIG. 1, in conjunction with other components of areduced pressure treatment system, such as components of reducedpressure treatment system 100 in FIG. 1. The process illustrated in FIG.5 provides illustrative embodiments and additional detail with respectto steps 415 and 420 in FIG. 4.

The process begins by determining whether the actual reduced pressureexceeds the target reduced pressure (step 505). If the processdetermines that the actual reduced pressure does not exceed the targetreduced pressure, the process terminates. Returning to step 505, if theprocess determines the actual reduced pressure exceeds the targetreduced pressure, the process decreases the generated reduced pressurethat is generated by the reduced pressure source (step 510).

The process determines whether the actual reduced pressure exceeds thetarget reduced pressure by a predetermined threshold (step 515). If theprocess determines that the actual reduced pressure does not exceed thetarget reduced pressure by the predetermined threshold, the processterminates. Returning to step 515, if the process determines that theactual reduced pressure exceeds the target reduced pressure by apredetermined threshold, the process determines whether to decrease thereduced pressure by opening a relief valve (step 520). If the processdetermines to decrease the reduced pressure by opening a relief valve,the process opens the relief valve to decrease the actual reducedpressure at the tissue site (step 525).

Returning to step 520, if the process determines not to decrease thereduced pressure by opening a relief valve, the process determineswhether to decrease the reduced pressure by turning off the reducedpressure source (step 530). If the process determines to decrease thereduced pressure by turning off the reduced pressure source, the processturns off the reduced pressure source (step 535). The process thenterminates. Returning to step 530, if the process determines not todecrease the reduced pressure by turning off the reduced pressuresource, the process terminates.

Turning to FIG. 6, a flowchart illustrating a process for managingreduced pressure at a tissue site is depicted in accordance with anillustrative embodiment of the present invention. The processillustrated in FIG. 6 may be implemented by a controller, such ascontroller 170 in FIG. 1, in conjunction with other components of areduced pressure treatment system, such as components of reducedpressure treatment system 100 in FIG. 1. The process illustrated in FIG.5 provides illustrative embodiments and additional detail with respectto steps 415 and 420 in FIG. 4.

The process begins by determining whether the target reduced pressureexceeds the actual reduced pressure (step 605). If the processdetermines that the target reduced pressure does not exceed the actualreduced pressure, the process terminates. Returning to step 605, if theprocess determines that the target reduced pressure exceeds the actualreduced pressure, the process increases the generated reduced pressurethat is generated by the reduced pressure source (step 610).

The process determines whether the actual reduced pressure measured bythe single pressure sensor is responsive to the increased generatedreduced pressure (step 615). If the process determines that the actualreduced pressure measured by the single pressure sensor is responsive tothe increased generated reduced pressure, the process terminates.Returning to step 615, if the process determines that the actual reducedpressure measured by the single pressure sensor is nonresponsive to theincreased generated reduced pressure, the process emits a signal usingan indicator (step 620). The process then terminates.

Turning now to FIG. 7, a flowchart illustrating a process for managingreduced pressure at a tissue site is depicted in accordance with anillustrative embodiment of the present invention. The processillustrated in FIG. 7 may be implemented by a controller, such ascontroller 170 in FIG. 1, in conjunction with other components of areduced pressure treatment system, such as components of reducedpressure treatment system 100 in FIG. 1. The process illustrated in FIG.7 provides illustrative embodiments and additional detail with respectto steps 615 and 620 in FIG. 6.

The process begins by determining whether the actual reduced pressure atthe tissue site increases within a predefined time period (step 705). Ifthe process determines that the actual reduced pressure at the tissuesite does not increase within a predefined time period, the processemits a signal using an indicator (step 710). The process thenterminates.

Returning to step 705, if the process determines that the actual reducedpressure at the tissue site increases within a predefined time period,the process determines whether the actual reduced pressure at the tissuesite meets the target reduced pressure within a predefined time period(step 715). If the process determines that the actual reduced pressureat the tissue site does not meet the target reduced pressure within apredefined time period, the process emits a signal using the indicator(step 710). The process then terminates. Returning to step 715, if theprocess determines that the actual reduced pressure at the tissue sitemeets the target reduced pressure within a predefined time period, theprocess then terminates.

The flowcharts and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of the apparatus and methods. In somealternative implementations, the function or functions noted in theblock may occur out of the order noted in the figures. For example, insome cases, two blocks shown in succession may be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

The illustrative embodiments may be configured to be a light weight andlow cost system that consumes less power than currently used reducedpressure treatment systems. The reductions in size and weight areparticularly important when the system is to be used to treatlow-severity wounds and wounds on ambulatory patients. These wounds andpatients require a system that is unobtrusive and lightweight so thatdiscomfort to the patient and hindrance of movement are minimized.

One way in which cost, weight, and power consumption are minimized isthrough the use of only one sensor to measure pressure. As previouslymentioned, traditional systems typically use two pressure sensors, oneto measure pressure at the tissue site and one to measure pressure atthe reduced pressure source. However, the elimination of the pressuresensor measuring pressure at the reduced pressure source allowssignificant reductions in the amount of electronic circuitry requiredand also the amount of power consumed by the system. Additionally, anycircuitry and software used to compare the two sensor readings iseliminated. In addition, the illustrative embodiments enable theapplication of a predefined reduced pressure to tissue, while providingdetection and notification of certain anomalous system conditions withfewer components than prior systems.

The illustrative embodiments also eliminate the need to approximate thetissue site pressure using a measured value at the reduced pressuresource. Further, determining the pressure directly at the tissue site,when included with the other features of the illustrative embodiments,allows the reduced pressure treatment system to detect leaks andblockages by observing pressure changes at the tissue site in responseto operational changes made at the reduced pressure source.

We claim:
 1. An apparatus for managing reduced pressure at a tissuesite, the apparatus comprising: a reduced pressure source that generatesreduced pressure, the reduced pressure being delivered to the tissuesite via a delivery tube; a single pressure sensor detecting an actualreduced pressure at the tissue site through a control tube that does notreceive fluids drawn from the tissue site by the reduced pressuresource; a controller configured to detect, without the use of the singlepressure sensor or any other pressure sensor, when the reduced pressuregenerated by the reduced pressure source is increased, the controllerfurther configured to determine a responsiveness of the actual reducedpressure measured by the single pressure sensor to an increase inreduced pressure generated by the reduced pressure source; an indicatoremitting a signal when the controller determines that the actual reducedpressure measured by the single pressure sensor is nonresponsive to theincrease in reduced pressure generated by the reduced pressure source;and wherein the responsiveness is determined by at least one of (1)monitoring whether the actual reduced pressure at the tissue siteincreases within a predefined period of time, and (2) monitoring whetherthe actual reduced pressure at the tissue site meets a target reducedpressure within a predefined period of time.
 2. The apparatus of claim1, wherein the reduced pressure source generates a decreased reducedpressure when the actual reduced pressure at the tissue site detected bythe single pressure sensor exceeds a target reduced pressure.
 3. Theapparatus of claim 1, further comprising: a relief valve coupled to thedelivery tube, the relief valve opening to decrease the actual reducedpressure at the tissue site when the actual reduced pressure at thetissue site detected by the single pressure sensor exceeds a targetreduced pressure by a predetermined threshold.
 4. The apparatus of claim1, wherein the reduced pressure source generates an increased reducedpressure when a target reduced pressure exceeds the actual reducedpressure at the tissue site detected by the single pressure sensor. 5.The apparatus of claim 1, further comprising: a control tube reliefvalve coupled to the control tube that relieves reduced pressure in thecontrol tube when a blockage is detected in the control tube.
 6. Theapparatus of claim 1, further comprising: a manifold, wherein the singlepressure sensor detects the actual reduced pressure at the tissue sitethrough the control tube via the manifold.
 7. The apparatus of claim 1,wherein the control tube is a first lumen, wherein the delivery tube isa second lumen, and wherein the first lumen and the second lumen are ina single multi-lumen tube.
 8. The apparatus of claim 1, wherein theindicator is a light emitting diode, and wherein the signal is anillumination of the light emitting diode.
 9. The apparatus of claim 1,wherein the apparatus includes no other pressure sensor other than thesingle pressure sensor.
 10. The apparatus of claim 1, wherein thereduced pressure source includes a motor having a speed.
 11. Theapparatus of claim 10, wherein a sensor detects the speed of the motor,and wherein the indicator emits the signal when the speed of the motorchanges by a threshold amount.
 12. The apparatus of claim 1, wherein thecontroller detects the increase in the reduced pressure generated by thereduced pressure source by detecting an increase in current draw by amotor associated with the reduced pressure source.
 13. The apparatus ofclaim 1, wherein the predefined period of time is in a range of 1 to 10seconds.
 14. The apparatus of claim 1, wherein the predefined period oftime is in a range of 4 to 6 seconds.